pragma solidity ^0.4.24;

contract Multiownable {

    bool public paused = false;
    uint256 public howManyOwnersDecide;
    address[] public owners;
    bytes32[] public allOperations;
    address internal insideCallSender;
    uint256 internal insideCallCount;

    mapping(address => uint) public ownersIndices; // Starts from 1
    mapping(bytes32 => uint) public allOperationsIndicies;

    mapping(bytes32 => uint256) public votesMaskByOperation;
    mapping(bytes32 => uint256) public votesCountByOperation;

    event OperationCreated(bytes32 operation, uint howMany, uint ownersCount, address proposer);
    event OperationUpvoted(bytes32 operation, uint votes, uint howMany, uint ownersCount, address upvoter);
    event OperationPerformed(bytes32 operation, uint howMany, uint ownersCount, address performer);
    event OperationDownvoted(bytes32 operation, uint votes, uint ownersCount,  address downvoter);
    event OperationCancelled(bytes32 operation, address lastCanceller);
    event OwnershipRenounced(address indexed previousOwner);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    event Pause();
    event Unpause();

    function isOwner(address wallet) public constant returns(bool) {
        return ownersIndices[wallet] > 0;
    }

    function ownersCount() public view returns(uint) {
        return owners.length;
    }

    function allOperationsCount() public  view returns(uint) {
        return allOperations.length;
    }

    modifier onlyAnyOwner {
        if (checkHowManyOwners(1)) {
            bool update = (insideCallSender == address(0));
            if (update) {
                insideCallSender = msg.sender;
                insideCallCount = 1;
            }
            _;
            if (update) {
                insideCallSender = address(0);
                insideCallCount = 0;
            }
        }
    }

    modifier onlyManyOwners {
        if (checkHowManyOwners(howManyOwnersDecide)) {
            bool update = (insideCallSender == address(0));
            if (update) {
                insideCallSender = msg.sender;
                insideCallCount = howManyOwnersDecide;
            }
            _;
            if (update) {
                insideCallSender = address(0);
                insideCallCount = 0;
            }
        }
    }

    constructor() public {  }

    function checkHowManyOwners(uint howMany) internal returns(bool) {
        if (insideCallSender == msg.sender) {
            require(howMany <= insideCallCount, "checkHowManyOwners: nested owners modifier check require more owners");
            return true;
        }

        uint ownerIndex = ownersIndices[msg.sender] - 1;
        require(ownerIndex < owners.length, "checkHowManyOwners: msg.sender is not an owner");
        bytes32 operation = keccak256(abi.encodePacked(msg.data));

        require((votesMaskByOperation[operation] & (2 ** ownerIndex)) == 0, "checkHowManyOwners: owner already voted for the operation");
        votesMaskByOperation[operation] |= (2 ** ownerIndex);
        uint operationVotesCount = votesCountByOperation[operation] + 1;
        votesCountByOperation[operation] = operationVotesCount;
        if (operationVotesCount == 1) {
            allOperationsIndicies[operation] = allOperations.length;
            allOperations.push(operation);
            emit OperationCreated(operation, howMany, owners.length, msg.sender);
        }
        emit OperationUpvoted(operation, operationVotesCount, howMany, owners.length, msg.sender);

        // If enough owners confirmed the same operation
        if (votesCountByOperation[operation] == howMany) {
            deleteOperation(operation);
            emit OperationPerformed(operation, howMany, owners.length, msg.sender);
            return true;
        }

        return false;
    }

    function deleteOperation(bytes32 operation) internal {
        uint index = allOperationsIndicies[operation];
        if (index < allOperations.length - 1) { // Not last
            allOperations[index] = allOperations[allOperations.length - 1];
            allOperationsIndicies[allOperations[index]] = index;
        }
        allOperations.length--;

        delete votesMaskByOperation[operation];
        delete votesCountByOperation[operation];
        delete allOperationsIndicies[operation];
    }

    function cancelPending(bytes32 operation) public onlyAnyOwner {
        uint ownerIndex = ownersIndices[msg.sender] - 1;
        require((votesMaskByOperation[operation] & (2 ** ownerIndex)) != 0, "cancelPending: operation not found for this user");
        votesMaskByOperation[operation] &= ~(2 ** ownerIndex);
        uint operationVotesCount = votesCountByOperation[operation] - 1;
        votesCountByOperation[operation] = operationVotesCount;
        emit OperationDownvoted(operation, operationVotesCount, owners.length, msg.sender);
        if (operationVotesCount == 0) {
            deleteOperation(operation);
            emit OperationCancelled(operation, msg.sender);
        }
    }


    function transferOwnership(address _newOwner, address _oldOwner) public onlyManyOwners {
        _transferOwnership(_newOwner, _oldOwner);
    }

    function _transferOwnership(address _newOwner, address _oldOwner) internal {
        require(_newOwner != address(0));

        for(uint256 i = 0; i < owners.length; i++) {
            if (_oldOwner == owners[i]) {
                owners[i] = _newOwner;
                ownersIndices[_newOwner] = ownersIndices[_oldOwner];
                ownersIndices[_oldOwner] = 0;
                break;
            }
        }
        emit OwnershipTransferred(_oldOwner, _newOwner);
    }

    modifier whenNotPaused() {
        require(!paused);
        _;
    }

    modifier whenPaused() {
        require(paused);
        _;
    }

    function pause() public onlyManyOwners whenNotPaused {

        paused = true;
        emit Pause();
    }

    function unpause() public onlyManyOwners whenPaused {
        paused = false;
        emit Unpause();
    }
}

contract GovernanceMigratable is Multiownable {
    mapping(address => bool) public governanceContracts;

    event GovernanceContractAdded(address addr);
    event GovernanceContractRemoved(address addr);

    modifier onlyGovernanceContracts() {
        require(governanceContracts[msg.sender]);
        _;
    }

    function addAddressToGovernanceContract(address addr) onlyManyOwners public returns(bool success) {
        if (!governanceContracts[addr]) {
            governanceContracts[addr] = true;
            emit GovernanceContractAdded(addr);
            success = true;
        }
    }

    function removeAddressFromGovernanceContract(address addr) onlyManyOwners public returns(bool success) {
        if (governanceContracts[addr]) {
            governanceContracts[addr] = false;
            emit GovernanceContractRemoved(addr);
            success = true;
        }
    }
}

contract BlacklistMigratable is GovernanceMigratable {
    mapping(address => bool) public blacklist;

    event BlacklistedAddressAdded(address addr);
    event BlacklistedAddressRemoved(address addr);

    function addAddressToBlacklist(address addr) onlyGovernanceContracts() public returns(bool success) {
        if (!blacklist[addr]) {
            blacklist[addr] = true;
            emit BlacklistedAddressAdded(addr);
            success = true;
        }
    }

    function removeAddressFromBlacklist(address addr) onlyGovernanceContracts() public returns(bool success) {
        if (blacklist[addr]) {
            blacklist[addr] = false;
            emit BlacklistedAddressRemoved(addr);
            success = true;
        }
    }
}

library SafeMath {

    function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {

        if (_a == 0) {
            return 0;
        }
        c = _a * _b;
        assert(c / _a == _b);
        return c;
    }
    function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
        return _a / _b;
    }

    function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
        assert(_b <= _a);
        return _a - _b;
    }

    function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        c = _a + _b;
        assert(c >= _a);
        return c;
    }
}

contract ERC20Basic {
    function totalSupply() public view returns (uint256);
    function balanceOf(address _who) public view returns (uint256);
    function transfer(address _to, uint256 _value) public returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
}

contract ERC20 is ERC20Basic {
    function allowance(address _owner, address _spender)
    public view returns (uint256);

    function transferFrom(address _from, address _to, uint256 _value)
    public returns (bool);

    function approve(address _spender, uint256 _value) public returns (bool);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

contract BasicToken is ERC20Basic {
    using SafeMath for uint256;

    mapping(address => uint256) internal balances;

    uint256 internal totalSupply_;

    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }

    function transfer(address _to, uint256 _value) public returns (bool) {
        require(_value <= balances[msg.sender]);
        require(_to != address(0));

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    function balanceOf(address _owner) public view returns (uint256) {
        return balances[_owner];
    }
}

contract StandardToken is ERC20, BasicToken {

    mapping (address => mapping (address => uint256)) internal allowed;

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    returns (bool)
    {
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);
        require(_to != address(0));

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }


    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }


    function allowance(
        address _owner,
        address _spender
    )
    public
    view
    returns (uint256)
    {
        return allowed[_owner][_spender];
    }


    function increaseApproval(
        address _spender,
        uint256 _addedValue
    )
    public
    returns (bool)
    {
        allowed[msg.sender][_spender] = (
        allowed[msg.sender][_spender].add(_addedValue));
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    function decreaseApproval(
        address _spender,
        uint256 _subtractedValue
    )
    public
    returns (bool)
    {
        uint256 oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue >= oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }
}

contract TruePausableToken is StandardToken, BlacklistMigratable {

    function transfer(
        address _to,
        uint256 _value
    )
    public
    whenNotPaused
    returns (bool)
    {
        require(!blacklist[msg.sender]);
        return super.transfer(_to, _value);
    }

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    whenNotPaused
    returns (bool)
    {
        require(!blacklist[_from]);
        return super.transferFrom(_from, _to, _value);
    }

    function approve(
        address _spender,
        uint256 _value
    )
    public
    whenNotPaused
    returns (bool)
    {
        return super.approve(_spender, _value);
    }

    function increaseApproval(
        address _spender,
        uint _addedValue
    )
    public
    whenNotPaused
    returns (bool success)
    {
        return super.increaseApproval(_spender, _addedValue);
    }

    function decreaseApproval(
        address _spender,
        uint _subtractedValue
    )
    public
    whenNotPaused
    returns (bool success)
    {
        return super.decreaseApproval(_spender, _subtractedValue);
    }
}

contract DetailedERC20 is ERC20 {
    string public name;
    string public symbol;
    uint8 public decimals;

    constructor(string _name, string _symbol, uint8 _decimals) public {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }
}

contract TrueBurnableToken is BasicToken {

    event Burn(address indexed burner, uint256 value);

    function _burn(address _who, uint256 _value) internal {
        require(_value <= balances[_who]);

        balances[_who] = balances[_who].sub(_value);
        totalSupply_ = totalSupply_.sub(_value);
        emit Burn(_who, _value);
        emit Transfer(_who, address(0), _value);
    }
}

contract KRWQToken is StandardToken, TrueBurnableToken, DetailedERC20, TruePausableToken {

    event Mint(address indexed to, uint256 amount);

    uint8 constant DECIMALS = 18;

    constructor(address _firstOwner,
                address _secondOwner,
                address _thirdOwner,
                address _fourthOwner,
                address _fifthOwner) DetailedERC20("KRWQ Stablecoin by Q DAO v1.0", "KRWQ", DECIMALS)  public {

        owners.push(_firstOwner);
        owners.push(_secondOwner);
        owners.push(_thirdOwner);
        owners.push(_fourthOwner);
        owners.push(_fifthOwner);
        owners.push(msg.sender);

        ownersIndices[_firstOwner] = 1;
        ownersIndices[_secondOwner] = 2;
        ownersIndices[_thirdOwner] = 3;
        ownersIndices[_fourthOwner] = 4;
        ownersIndices[_fifthOwner] = 5;
        ownersIndices[msg.sender] = 6;

        howManyOwnersDecide = 4;
    }

    function mint(address _to, uint256 _amount) external onlyGovernanceContracts() returns (bool){
        totalSupply_ = totalSupply_.add(_amount);
        balances[_to] = balances[_to].add(_amount);
        emit Mint(_to, _amount);
        emit Transfer(address(0), _to, _amount);
        return true;
    }

    function approveForOtherContracts(address _sender, address _spender, uint256 _value) external onlyGovernanceContracts() {
        allowed[_sender][_spender] = _value;
        emit Approval(_sender, _spender, _value);
    }

    function burnFrom(address _to, uint256 _amount) external onlyGovernanceContracts() returns (bool) {
        allowed[_to][msg.sender] = _amount;
        transferFrom(_to, msg.sender, _amount);
        _burn(msg.sender, _amount);
        return true;
    }
}